Our research group focuses on physics and applications of nanomechanical devices. Activities in this lab include fabrication of resonant nanomechanical devices with frequencies in the very high and ultra-high frequency range, novel transduction and actuation schemes, study of noise processes that govern the frequency stability and the utility of these devices for various applications.


Fundamental research in NEMS 

Nanoelectromechanical systems (NEMS) offer an exciting platform to study the most fundamental dynamical phenomena in nature. We use these systems to study the nonlinear dynamics of the coupled modes of a nanomechanical resonator and synchronization between these modes. We have recently developed a technique that allows us to tune the coupling between various modes of the resonator. If the coupling is very weak, we can study synchronization, and if the coupling is substantial, we can study internal resonance between different modes. As we have precise control over the coupling, we can observe the system’s behavior during the transition from weakly coupled to strongly coupled regimes. 



Integration of mechanical elements on a silicon photonic chip introduces additional functionality, with applications in fundamental research as well as in sensing, signal processing, and communication. We develop on-chip optomechanical systems in this platform using silicon as well as 2D materials and study interactions between optical and mechanical resonators. In these systems, we develop sensitive motion-readout mechanisms and evaluate external stimuli sensitivity for applications as sensors. We are exploring on-chip optical transduction schemes in these systems as they offer higher sensitivity and signal-to-noise ratio than the conventional electrical transduction schemes used in MEMS/NEMS devices. We are looking at ways to explore quantum phenomena in optomechanical systems. 



These nanomechanical devices on account of their minute size are extremely sensitive to the changes in their properties. These devices have been used for various applications from pressure sensing to mass spectrometry. The current state-of-the-art top down fabricated devices are limited to experimental mass resolutions of about 100kDa. These resolutions have led to some promising results in the area of neutral mass spectrometry and virus capsid studies with analyte masses in the range of MDa. However, a large fraction of the protein masses is below 100kDa and it is crucial that the resolution be below a single Dalton for proteomics applications. This would require fabricating devices with smaller dimensions and consequently, resonant frequencies in 100MHz to GHz range. However, for these smaller and stiffer devices the displacement amplitudes are typically smaller and can be less than picometers. The electrical transduction schemes that are efficient at large scales fail due to issues related to impedance mismatch, parasitic capacitance and poor bandwidth. Furthermore, since the overall dimension of the device is small, the capture cross section of detection is extremely low. Scaling up the electrical transduction scheme would require complex interconnects.

Our group is exploring optical and other transduction schemes that might result in better displacement sensitivities and larger bandwidth, both of which are critical for sensing applications. One of the schemes being explored is to leverage advances in Silicon photonics to integrate on-chip optics with nanomechanical devices. Optical displacement sensitives have been experimentally demonstrated to be in the range of , have large bandwidths and have signals have minimal background. They are also exploring the use of graphene and other 2D materials to transduce motion of mechanical resonators fabricated using conventional materials such as silicon nitride.

Some the applications being pursued are pressure sensors based on 2D materials, gas sensing and switching using nanomechanical bifurcation amplifier.


We explore the piezoelectric properties of 2D materials for applications in sensors and piezotronic devices. To this end, we fabricate and characterize 2D material-based devices. We have proposed a new technique to quantitatively measure the in-plane piezoelectric coupling for 2D materials using lateral PFM (Piezo Force Microscopy). Also, we devise methods to fabricate the piezotronic devices on flexible substrates such as PET and Kapton. Through this work, we aim to contribute to developing a new generation of interactive electronic devices. 



Atomic Force Microscopy

The invention of Scanning Probe Microscopy techniques has opened the doors to the nanoworld. We have been using Atomic ForceMicroscopy (AFM) for different nanomechanical studies. We use force spectroscopy in AFM to study the mechanics of ultrathin suspended membranes. We explore the fundamental nature of tip-sample interaction for different materials in dynamic AFM to understand the coupling between the oscillating tip and sample effectively. We have also explored capillary condensation that can occur in AFM imaging of confined structures like nanopores. Currently, we are investigating graphene-liquid interface through nanomechanical probing with dynamic AFM. Our goal in this study is to gain insights into the fundamental nature of forces at the graphene-liquid interface.